The Callanish Stones on the island of Lewis and Harris date from prehistoric times. There are so many standing stones that they are difficult to count. The site dates back to the late Stone Age and early Bronze Age (3000-1500 BCE), making it roughly contemporary with Stonehenge in England. The group of stones forms a circle with alignments radiating outwards at the compass points. The site is one of a series that used to exist in the vicinity and are generally thought to have been used for astronomical observations.